Better errors for Blazor asset integrity problems

src/Components/Shared/src/ResourceCollectionProvider.cs

@@ -54,8 +54,19 @@ private async Task<ResourceAssetCollection> LoadResourceCollection()
             return ResourceAssetCollection.Empty;
         }
 
-        var module = await _jsRuntime.InvokeAsync<IJSObjectReference>("import", _url);
-        var result = await module.InvokeAsync<ResourceAsset[]>("get");
-        return result == null ? ResourceAssetCollection.Empty : new ResourceAssetCollection(result);
+        try
+        {
+            var module = await _jsRuntime.InvokeAsync<IJSObjectReference>("import", _url);
+            var result = await module.InvokeAsync<ResourceAsset[]>("get");
+            return result == null ? ResourceAssetCollection.Empty : new ResourceAssetCollection(result);
+        }
+        catch (Exception ex)
+        {
+            throw new InvalidOperationException(
+                $"Failed to load the Blazor resource collection from '{_url}'. " +
+                "This is likely caused by a mismatch in the file integrity check, which can happen when files are modified after they are published. " +
+                "Ensure that all published files are deployed correctly and that none have been modified after publish.",
+                ex);
+        }
     }
 }

src/Components/WebAssembly/WebAssembly/src/Hosting/HostedServiceExecutor.cs

@@ -45,7 +45,7 @@ public async Task StopAsync(CancellationToken token)
         // Throw an aggregate exception if there were any exceptions
         if (exceptions is not null)
         {
-            var aggregateException = new AggregateException(exceptions);
+            var aggregateException = new AggregateException("One or more hosted services failed to stop.", exceptions);
             try
             {
                 Log.ErrorStoppingHostedServices(_logger, aggregateException);

src/Components/WebAssembly/WebAssembly/test/Hosting/HostedServiceExecutorTest.cs

@@ -0,0 +1,58 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace Microsoft.AspNetCore.Components.WebAssembly.Hosting;
+
+public class HostedServiceExecutorTest
+{
+    [Fact]
+    public async Task StopAsync_WithFailingServices_ThrowsAggregateExceptionWithDescriptiveMessage()
+    {
+        // Arrange
+        var services = new[]
+        {
+            new FaultyHostedService("Service 1 error"),
+            new FaultyHostedService("Service 2 error"),
+        };
+        var executor = new HostedServiceExecutor(services, NullLogger<HostedServiceExecutor>.Instance);
+
+        // Act
+        var ex = await Assert.ThrowsAsync<AggregateException>(() => executor.StopAsync(CancellationToken.None));
+
+        // Assert
+        Assert.StartsWith("One or more hosted services failed to stop.", ex.Message);
+        Assert.Equal(2, ex.InnerExceptions.Count);
+    }
+
+    [Fact]
+    public async Task StopAsync_WithNoFailingServices_DoesNotThrow()
+    {
+        // Arrange
+        var services = new[]
+        {
+            new SuccessfulHostedService(),
+            new SuccessfulHostedService(),
+        };
+        var executor = new HostedServiceExecutor(services, NullLogger<HostedServiceExecutor>.Instance);
+
+        // Act (should not throw)
+        await executor.StopAsync(CancellationToken.None);
+    }
+
+    private class FaultyHostedService(string errorMessage) : IHostedService
+    {
+        public Task StartAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+
+        public Task StopAsync(CancellationToken cancellationToken) =>
+            Task.FromException(new InvalidOperationException(errorMessage));
+    }
+
+    private class SuccessfulHostedService : IHostedService
+    {
+        public Task StartAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+        public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+    }
+}

src/Components/WebAssembly/WebAssembly/test/ResourceCollectionProviderTest.cs

@@ -0,0 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.JSInterop;
+using Moq;
+
+namespace Microsoft.AspNetCore.Components;
+
+public class ResourceCollectionProviderTest
+{
+    [Fact]
+    public async Task GetResourceCollection_WhenUrlIsNull_ReturnsEmpty()
+    {
+        // Arrange
+        var jsRuntime = Mock.Of<IJSRuntime>();
+        var provider = new ResourceCollectionProvider(jsRuntime);
+
+        // Act
+        var result = await provider.GetResourceCollection();
+
+        // Assert
+        Assert.Same(ResourceAssetCollection.Empty, result);
+    }
+
+    [Fact]
+    public async Task GetResourceCollection_WhenImportFails_ThrowsDescriptiveError()
+    {
+        // Arrange
+        var url = "/_framework/resource-collection.abc123.js";
+        var jsRuntime = new Mock<IJSRuntime>();
+        jsRuntime
+            .Setup(r => r.InvokeAsync<IJSObjectReference>("import", It.IsAny<object[]>()))
+            .ThrowsAsync(new JSException("Failed to fetch dynamically imported module"));
+
+        var provider = new ResourceCollectionProvider(jsRuntime.Object);
+        provider.ResourceCollectionUrl = url;
+
+        // Act
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => provider.GetResourceCollection());
+
+        // Assert
+        Assert.Contains($"Failed to load the Blazor resource collection from '{url}'", ex.Message);
+        Assert.Contains("integrity", ex.Message, StringComparison.OrdinalIgnoreCase);
+        Assert.NotNull(ex.InnerException);
+        Assert.IsType<JSException>(ex.InnerException);
+    }
+
+    [Fact]
+    public async Task GetResourceCollection_WhenGetFails_ThrowsDescriptiveError()
+    {
+        // Arrange
+        var url = "/_framework/resource-collection.abc123.js";
+        var jsRuntime = new Mock<IJSRuntime>();
+        var moduleReference = new Mock<IJSObjectReference>();
+
+        jsRuntime
+            .Setup(r => r.InvokeAsync<IJSObjectReference>("import", It.IsAny<object[]>()))
+            .ReturnsAsync(moduleReference.Object);
+
+        moduleReference
+            .Setup(m => m.InvokeAsync<ResourceAsset[]>("get", It.IsAny<object[]>()))
+            .ThrowsAsync(new JSException("An error occurred"));
+
+        var provider = new ResourceCollectionProvider(jsRuntime.Object);
+        provider.ResourceCollectionUrl = url;
+
+        // Act
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => provider.GetResourceCollection());
+
+        // Assert
+        Assert.Contains($"Failed to load the Blazor resource collection from '{url}'", ex.Message);
+        Assert.Contains("integrity", ex.Message, StringComparison.OrdinalIgnoreCase);
+        Assert.NotNull(ex.InnerException);
+        Assert.IsType<JSException>(ex.InnerException);
+    }
+}